On Glide and Creep of the Snow Cover Among Avalanche Defenses

On_Glide_and_Creep_of_the_Snow_Cover_Among_Avalanche_Defenses - Page 4

the task of investigating the snow cover movements in several avalanche defenses of the fore- Alp region. In addition to published works, an especially valuable basic source has been the Winter Reports on the defenses and afforestation project " Schilt'VStein which has appeared annually since 19^ 6. Obser­vations at the other mentioned defenses are set forth in the Internal Reports of the Swiss Federal Institute for Snow and Avalanche Research. These would not have been possible without the substantial and praise­worthy assistance of the local forest organizations. The V/ eather Conditions As a rule, the snow cover glides over the ground at lower altitudes in the Swiss Alps. The amount of glide depends on surface conditions, slope angles, and slope exposures. In addition to the orographic con­ditions, the weather and snow cover accumulation play important roles. It is only when favorable weather conditions prevail that exceptional gliding occurs with heavy damage. If we analyze the weather for the three glide winters 1952/ 53, 1965/ 66 and 1966/ 67, we encounter several parallels. The most outstanding criterion is heavy snowfalls early in the winter with a rapid accumulation of a deep snow cover. If the early snowfalls were preceded by a warm summer or fall, the gliding is increased The weather summaries of the Central Meteorological Office ( MZA) ( 1) for the three winters ran as follows. November 1952: The region